Integrated intensity of the SiO(2−1) transition against the shock velocity calculated over the n_H = 10⁴ cm^-3 fragment of our grid of models (colored symbols), and compared to the observations (thick, horizontal black line, obtained in position 1, with thinner lines corresponding to ± 15% uncertainty; see Tables 7 and 8). The left and right panels correspond to the SiG (square symbols) and SiM (circle symbols) scenarios (see text). The color code is indicated in the panels, where the G₀ (=0 or 1) value and fraction of preshock free silicon (=1 or 10%) is shown for each model.